Interferon is a class of immunomodulators that possess an anti-viral activity. Based on their functions and protein structures, there are three types of interferons (type I, type II and type III). Type-III interferon family comprises three members; namely, IFN-λ1, IFN-λ2 and IFN-λ3 that share a high degree of homology. Type-III IFNs represent the most recently identified interferons (Sheppard et al., 2003; Kotenko et al., 2003); therefore, many aspects of their regulation and function are unclear. IFN-λ proteins are encoded by three separate respective IFN-λ genes, which are all located on chromosome 19q13. The genomic nucleotide sequences upstream from the start codon for IFN-λ1, IFN-λ2 and IFN-λ3 have been reported. However, the regulatory elements of these genomic upstream structures have not been defined. The high sequence homology (˜95%) between the IFN-λ2 and IFN-λ3 upstream regions render the regulatory study for these promoters difficult. IFN-λ1 has a relatively diverse sequence (˜70%) compared to IFN-λ2 and IFN-λ3 promoters, but attempts in characterizing the regulatory elements of the IFN-λ1 promoter has only limited success.
Several research groups have examined the IFN-λ1 promoter. Despite these studies, the regulation of the IFN-λ1 promoter is far from clear; let alone the structural organization and the role of transcription sites in the IFN-λ1 promoter. Onoguchi et al. identified a ˜600 bp upstream region containing one (1) NF-κB and three (3) IRF sites that activates IFN-λ1 gene expression in murine fibrosarcoma cells in response to NewCastle disease virus stimulation (Onoguchi et al., 2007). In a similar vein, Osterlund et al. showed that transfection of human embryonic kidney cells with plasmids encoding NF-κB or IRF protein increases IFN-λ1 reporter gene activity (Osterlund et al., 2007). Thomson et al. examined a further upstream region (˜1.1 kb from the IFN-λ1 translation start codon) and discovered three (3) additional NF-κB sites. Using siRNA, this group showed a role of NF-κB in activation of IFN-λ1 gene expression in response to bacterial stimulation (Thomson et al., 2009). Given that IFN-λ1 is not constitutively expressed in human but induced following viral/bacterial stimulation, it is possible that there exists a repressor mechanism (yet to be uncovered) that keeps the IFN-λ1 expression at bay. To the best of the inventors' knowledge, there is simply no scientific support for this contention.
Accordingly, there is a continuing need in defining the regulatory elements of IFN-λ1 promoter and means to regulate the IFN-λ1 promoter activity. The present invention cures the deficiency of these prior art. The present inventors surprisingly discovered a novel repressor region between (˜1.2 kb and ˜1.6 kb from the IFN-λ1 translation start site) in the IFN-λ1 gene, and provide a novel means to regulate the IFN-λ1 promoter activity using siRNA against specific regions (BLIMP-1 and ZEB1) of the repressor. The present invention has practical utility in the treatment of viral infection and asthma.
Other features and advantages of the invention will be apparent from the following description of the embodiments discussed in the detailed description, and from the claims.